Re: [PATCH 1/4] btrfs: inline checksum name and driver definitions

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

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On 2020/2/28 上午4:00, David Sterba wrote:
> There's an unnecessary indirection in the checksum definition table,
> pointer and the string itself. The strings are short and the overall
> size of one entry is now 24 bytes.
> 
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
>  fs/btrfs/ctree.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
> index f948435e87df..bfedbbe2311f 100644
> --- a/fs/btrfs/ctree.c
> +++ b/fs/btrfs/ctree.c
> @@ -31,8 +31,8 @@ static void del_ptr(struct btrfs_root *root, struct btrfs_path *path,
>  
>  static const struct btrfs_csums {
>  	u16		size;
> -	const char	*name;
> -	const char	*driver;
> +	const char	name[10];

Just a nitpick, the longest name I haven seen is "xxhash64" which is
only 8 chars, +1 for '\n'.
Thus we can save one extra byte here.

Despite that.

Reviewed-by: Qu Wenruo <wqu@suse.com>

Thanks,
Qu
> +	const char	driver[12];
>  } btrfs_csums[] = {
>  	[BTRFS_CSUM_TYPE_CRC32] = { .size = 4, .name = "crc32c" },
>  	[BTRFS_CSUM_TYPE_XXHASH] = { .size = 8, .name = "xxhash64" },
> @@ -63,7 +63,8 @@ const char *btrfs_super_csum_name(u16 csum_type)
>  const char *btrfs_super_csum_driver(u16 csum_type)
>  {
>  	/* csum type is validated at mount time */
> -	return btrfs_csums[csum_type].driver ?:
> +	return btrfs_csums[csum_type].driver[0] ?
> +		btrfs_csums[csum_type].driver :
>  		btrfs_csums[csum_type].name;
>  }
>  
> 


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